Anatomical mapping of Merkel cells in normal human adult epidermis.

The distribution of Merkel cells (MCs) in normal human skin and mucosa was studied using the mouse monoclonal antibody Troma-1, reacting specifically with component 8 of the Moll cytokeratin catalogue. The specificity of this antibody for MCs in human skin was assessed by double indirect immunofluorescence (IIF) and immunoelectron microscopy. Two-hundred and thirty 6-mm punch biopsies were obtained from 44 different sites from six human cadavers within 48 h post-mortem. IIF was performed with Troma-1 on EDTA-split epithelial sheets and the MCs were counted and the mean values per mm2 calculated for each site. Regions with greater than 50 MC/mm2 were the lips, hard palate, palms, finger pads, proximal nail fold, and dorsum of the feet. Three different patterns were observed in the epidermis or mucosa: MCs grouped in clumps, linear and arciform arrangements, and scattered MCs. In the hair follicles grouped MCs were observed in the bulb and scattered MCs were seen in the outer root sheath.